A.G. Davydov, E.V. Smolyarchuk, N.K. Tkachev
ABSTRACT
A method to take into account polarization interactions between ions in molten salts by means of thermodynamic perturbation theory based on the model of a mixture of charged hard spheres with different diameters is presented. The basis for using such reference model is the observation for partial structural factors in liquid salts above the melting point. The inclusion of polarization interactions can be implemented in the framework of thermodynamic perturbation theory. Explicit expressions for the additional polarization term to the energy of salts are obtained in this work. On this basis, the influence of polarization contribution on the thermodynamic properties and melting characteristics of cesium-halide melts is considered. We have showed that the inclusion of polarization interactions between salt ions leads to decrease in the melting temperature and heat content of the melts as compared with the reference system of charged hard spheres. The errors in determining the melting temperatures of these salts without fitting the parameters of pair potential don’t exceed three percent. Accounting for the polarization contribution to free energy provides a more accurate description of the enthalpies and entropies of melting.
KEYWORDS:
polarizability, charged hard spheres, thermodynamic perturbation theory, mean spherical approximation, alkali metal halides, melting temperature, enthalpy of melting, heat content, phase equilibria.
DOI:10.1134/S0235010619060021